Acyclovir (9-(2-hydroxyethoxymethyl) guanine) is one of a new class of antiviral compounds shown to be effective in a variety of herpesvirus infections. It has been recently found in this laboratory that the drug is also effective in inhibiting Epstein-Barr Virus (EBV) replication. In this poject we propose to study the effect of this drug on EBV replication and determine its mode of action in the inhibition of EBV DNA synthesis.